AtLeast compares the local version to a minimum version.
LocalCopy copies a directory using rsync (with the --devices option).
func Recv(path string, conn io.ReadWriteCloser, tracker *ioprogress.ProgressTracker, features string) error
Recv sets up the receiving half of the websocket to rsync (the other half set up by rsync.Send), putting the contents in the directory specified by path.
func Send(name string, path string, conn io.ReadWriteCloser, tracker *ioprogress.ProgressTracker, features string, bwlimit string, execPath string, rsyncArgs ...string) error
Send sets up the sending half of an rsync, to recursively send the directory pointed to by path over the websocket.